Agriculture - An Overview

Techniques aimed at crop improvement have been utilized for centuries. Today, applied plant science has three overall goals: increased crop yield, improved crop quality, and reduced production costs. Biotechnology is proving its value in meeting these goals. Progress has, however, been slower than with medical and other areas of research. Because plants are genetically and physiologically more complex than single-cell organisms such as bacteria and yeasts, the necessary technologies are developing more slowly.

Improvements in Crop Yield and Quality

In one active area of plant research, scientists are exploring ways to use genetic modification to confer desirable characteristics on food crops. Similarly, agronomists are looking for ways to harden plants against adverse environmental conditions such as soil salinity, drought, alkaline earth metals, and anaerobic (lacking air) soil conditions.

Genetic engineering methods to improve fruit and vegetable crop characteristics - such as taste, texture, size, color, acidity or sweetness, and ripening process, are being explored as a potentially superior strategy to the traditional method of cross-breeding.

Research in this area of agricultural biotechnology is complicated by the fact that many of a crop's traits are encoded not by one gene but by many genes working together. Therefore, one must first identify all of the genes that function as a set to express a particular property. This knowledge can then be applied to altering the germlines of commercially important food crops. For example, it will be possible to transfer the genes regulating nutrient content from one variety of tomatoes into a variety that naturally grows to a larger size. Similarly, by modifying the genes that control ripening, agronomists can provide supplies of seasonal fruits and vegetables for extended periods of time.

Biotechnological methods for improving field crops, such as wheat, corn and soybeans, are also being sought, since seeds serve both as a source of nutrition for people and animals and as the material for producing the next plant generation. By increasing the quality and quantity of protein or varying the types in these crops, we can improve their nutritional value. For example, a major protein of corn has very little of two amino acids, lysine and tryptophan, which are essential for human growth. Increased amounts of these amino acids could make corn products a source of improved protein.

Biopesticides and Biofertilizers

Biotechnology makes it possible to develop bacteria essential to herbicide and other pesticide compounds. Certain chemicals produced by these organisms are called allelopathic agents. These chemicals act as natural herbicides, preventing the growth of other plant species in the same geographic area. Black walnut trees, for example, release an allelopathic agent against tomato plants.

Modern high-yield agriculture entails consumption of vast amounts of chemicals for use as fertilizers and as agents to control pests and plant diseases, and any means that will permit the plant to do this work itself could result in significant savings for the farmer. For example, soybeans and certain other legumes produce their own source of usable nitrogen fertilizer by a process known as nitrogen fixation. This process is made possible by a bacterium that grows symbiotically on the plant's roots. (In a symbiotic relationship, dissimilar organisms live together in a mutually beneficial way.) In the nitrogen-fixing process, microbes capture atmospheric nitrogen and biochemically convert it into water-soluble nitrogen. This form of nitrogen is an essential nutrient for increasing the quantity and quality of plant yield.

This bacteria will not assist in the growth of other important crops, such as corn and cereal plants. But research on nitrogen-fixing bacteria and legumes may show how we can modify either the bacteria or non-leguminous plants, thereby making many crops more nearly self-sufficient in obtaining nitrogen.

Biotechnology is central to the search for effective, environmentally safe and economically sound alternatives to chemical pesticides. Biotechnology may be used to protect commercial crop plants from insect pests and promises to guard against further environmental deterioration and to provide a useful alternative to traditional methods of insect pest control.

Biopesticides degrade rapidly in the environment - a major environmental benefit. The active elements of bacterial pesticides are proteins that are fragile molecules. Once exposed to the sun and other natural elements, these proteins are quickly broken down, thereby prohibiting spread to groundwater and other animal and plant species. This will help keep our water supply safe to drink, our lakes and streams habitable for water life and recreation.

Unlike chemical pesticide technology, biopesticide technology is based on potent, naturally occurring proteins. These living particles are produced in nature by microorganisms such as Bacillus thuringiensis (B.t.). Discovered at the turn of the century, B.t. has been used without risk in the United States for almost three decades by home gardeners, farmers, and forestry officials. Its active component, a protein, specifically attacks the stomachs of target pests, disrupting their digestive tracks so thoroughly that the pests stop eating and eventually die of starvation. Higher organisms, such as mammals, fish, birds, and other non-target species remain unthreatened, however, because their stomach acid easily breaks down the protein toxin.

The delivery of these biopesticides varies in method and design. In one method, dormant spores of B.t. are dusted on crops. The spores then become active and multiply, covering plants with a bacteria poisonous to the target insects that feed on them. The B.t. toxin gene can also be inserted into the genetic makeup of crops, giving them a built-in resistance to insects. Similarly, the toxin gene can be put into a third party, such as a microorganism that lives within the plant's sap. These organisms - known as endophytes - multiply within the host plant and move throughout the plant's vascular system, forming a microscopic defense against feeding insects. This process resembles vaccines moving throughout a person's vascular system to defend against harmful disease.

Some of the concerns farmers raise about having to use increasingly dangerous pesticides to produce adequate crops may well be addressed by biotechnology. Further research in agricultural biotechnology and biopesticide development aims to provide attractive alternatives to the farmer that will lower overall unit cost of production and allow the farmer to be more competitive in the highly cost-sensitive world markets. While some uses of chemical pesticides will be necessary for decades to come, continued development by biotechnology companies of useful biological pesticides will offer farmers viable alternatives.